The present invention relates to manufacturing a semiconductor integrated circuit device and, more particularly, to an extremely thin surface-mounted type resin-sealed package. In recent years, a semiconductor integrated circuit device equipped with the surface-mounted type resin-sealed package IC is used in a wide variety of fields because it can be packaged thinly and densely on a printed circuit board. Moreover, the surface-mounted type resin-sealed package IC is required to have a smaller thickness in accordance with recent technical innovation. On the other hand, a semiconductor chip to be encapsulated in the package of the surface-mounted type resin-sealed package IC has a larger planar size.
In the prior art, the surface-mounted type resin-sealed package IC is encapsulated by using a transfer molding machine. This transfer molding machine is constructed to include: a pair of upper and lower molds to be opened and closed; a cavity formed between the mating faces of the upper and lower molds and having a gate opening; a pot formed in the upper or lower mold; a runner formed in the upper or lower mold face for establishing communication between the pot and the gate; and a heater for heating and melting tablets of a molding material introduced into the pot.
In case a package is to be encapsulated by using the transfer molding machine, a lead frame having a semiconductor chip adhered thereto is set at first in the cavity with the upper and lower molds being opened, and this cavity is then pressure charged with a resin or molding material. Prior to a step for encapsulating a semiconductor chip, the semiconductor chip is bonded to tabs of the lead frame, and the individual leads of the lead frame and the bonding pads of the semiconductor chip are electrically connected by wires.
When the semiconductor chip is set in the cavity, the upper and lower molds are clamped to seal the lead frame between them. After this mold clamping, the tablets are introduced into the mold pot. The tablets thus introduced are heated and melted into a resin or a liquid molding material by the heaters, which are in the upper and lower molds. This molten resin is extruded from the pot to the runner by a plunger. The resin thus extruded runs from the gate to fill the cavity. The liquid resin in the cavity is set to a solid molding material by the cross-linking reaction resulting from the heating. The resin-sealed package is thus molded of the set solid molding material.
The tablets are prepared by kneading a molding material containing an epoxy resin as a base component, by pulverizing the kneaded material and by stamping the powdery molding material into a cylindrical shape. The resin is prepared by heating the tablet to melt the molding material into a liquid state. In short, in the transfer molding machine, the solid tablet is heated outside of the cavity to form the liquid resin, and this liquid resin is fed from the outside to the inside of the cavity.
An IC for realizing an extremely thin shape is exemplified by an "IC of TAB structure", in which the chip and the leads are connected electrically and mechanically by tape automated bonding (TAB). In this IC of TAB structure, the connected portions of the chip and the leads are resin-sealed with resins which is molded by potting. A resin-molding process in this IC of TAB structure is exemplified by the resin-sealed package molding process, as will be described in the following.
The solid resin is placed on the semiconductor chip that is preautomated-bonded to the leads. If, in this state, the semiconductor chip is guided through a hot-air drying furnace or a heated tunnel furnace, the solid resin is melted so that it softens and flows to cover the connected areas of the semiconductor chip and the leads. The covering resin is set later to form the resin-coated package. This resin-coated package has an extremely small thickness in its entirety because what is covered by resin is limited to the connected portions between the semiconductor chip and the leads in the vicinity of the chip.
The following patent specifications disclose the technology of covering the connected areas of the semiconductor chip and the lead group by melting a solid resin: Japanese Patent Laid-Open Nos. 39558/1982, 148360/1982, 18931/1983, 122757/1983 and 165333/1983.